The present invention relates to a hill-hold control (HHC) system, specifically to a hill-hold control system that dynamically adjusts braking pressure to the wheels of a vehicle (and a trailer if the vehicle is towing the trailer) to limit the amount of pressure to what is needed to hold the vehicle in place.
Current HHC functions hold pressure uniformly for all four wheels equally, including trailer brakes if a trailer is connected. The pressure is applied at the level requested by a driver through a brake pedal. There are two shortcomings of this control strategy. First, the strategy does not consider that a driver often over-brakes a vehicle, so more pressure is applied than required. Holding more pressure requires more current to control a switchover valve (USV) coil, thus increasing the durability required for the valve, and introducing noise-vibration-heat (NVH) issues due to valve activation.
Second, the strategy holds pressure in all hydraulic circuits equally, where a hydraulic unit can have different USV valves in different hydraulic circuits (e.g., front wheels versus rear wheels), and the filet it may be optimal to control different wheels using different pressure levels.